Archive

Archive for April, 2010

Voice – Packet Overhead

April 27th, 2010 No comments

Planning for Voice over IP requires an understanding of the various headers added when transporting packetised voice, espcially over an IPSec VPN: Read more…

Categories: Network Design, QoS, Voice over IP Tags: , ,

The Capture Buffer (or “sniffing”) on Cisco IOS

April 25th, 2010 No comments

A great alternative to SPAN and RSPAN, is to use the actual IOS itself as the packet sniffer! Capture traffic from the CLI and when you need to, export the data as a “.cap” (Wireshark, etc) file. to your PC. Read more…

Categories: CISCO Tags:

Robert Metcalfe – Inventor of Ethernet

April 22nd, 2010 No comments

Who invented Ethernet? Robert Metcalfe got the idea for the Ethernet protocol when he read a 1970 computer conference paper by Norman Abramson of the University of Hawaii about the packet radio system called ALOHAnet linking the Hawaiian Islands: Read more…

Categories: Uncategorized Tags:

QoS – Ingress and Egress Queuing using 2Q3T or 1P1Q3T

April 20th, 2010 No comments

1P1Q3T – ingress queuing
As switch platforms have architectures based on oversubscription, they have been engineered to guarantee QoS by protecting critical traffic trying to access the backplane/stack-ring via ingress queuing. Read more…

Categories: CISCO, QoS Tags:

QoS – 1P3Q3T Queuing

April 20th, 2010 No comments

The Cisco 2960, 2970, 3560 and 3750 Catalyst switches support a 1p3q3t que model which provides 3 thresholds in which to drop traffic. Read more…

Categories: CISCO, QoS Tags:

Cisco QoS Baseline (interim)

April 19th, 2010 No comments

Deciding upon a QoS Classification and Marking strategy can be a difficult task. Cisco have provided certain recommendations which may be implemented as a baseline QoS strategy and then altered over time: Read more…

Categories: Network Design, QoS Tags:

Basic QoS Model

April 19th, 2010 No comments

The basic QoS Model

The Basic QoS Model

Actions at the ingress interface include classifying traffic, policing, and marking: Read more…

Categories: Network Design, QoS Tags:

QoS – DSCP Classification Guidelines (RFC 4594)

April 19th, 2010 No comments

RFC 4594 describes some example and provides guidelines for DiffServ service classification which may be used as guidelines or as a basis for a QoS Classification Strategy: Read more…

Categories: Network Design, QoS Tags:

Modular QoS CLI (MQC)

April 19th, 2010 No comments

The Modular QoS CLI (MQC) command structure found in Cisco IOS® Software requires a class map is built incorporating the ACLs that identify the traffic that will have QoS applied to them. Read more…

Categories: Network Design Tags: ,

QoS – Classification and Marking

April 19th, 2010 No comments

The first element to a QoS policy is to classify/identify the traffic that is to be treated differently.  Following classification, certain “marking tools” can set an attribute of a frame or packet to a specific value. Such marking (or remarking) establishes a trust boundary that scheduling tools later depend on. Read more…

Categories: Network Design, QoS Tags: